The present invention relates to a seal assembly releasing tool and, more particularly, to a releasing tool which may be landed on a casing hanger seal assembly of a well, such as an oil well, and rotated in one direction to lock with the casing hanger seal assembly thus permitting the tool to rotate in the opposite direction for releasing the seal assembly from the outer well head casing.
In conventional wells including oil wells used for subsea drilling, it is common to use an outer well head casing through which is run an inner well head casing. As the subsea wells often extend some 6,000 feet to the sea floor, it is necessary to assemble the riser runs in sections. In order to do this, it is clear that means must be provided for connecting and sealing the inner and outer well head casings.
After the outer well head casing has been assembled by bolting or otherwise fastening the casings together, the inner well head casing is lowered one section at a time to the sea floor. As each inner well head casing is put into its desired position, a casing hanger member, attached to the top of the inner well head casing is landed on a shoulder formed on the inner surface of the outer well head casing and latched thereto by resilient means, for example.
The casing hanger may then be cemented into its desired position by use of a so called land and cement casing hanger tool. One example of a tool for landing an assembly which incorporates the casing hanger with a seal is shown in U.S. Pat. No. 3,273,646, which issued Sept. 20, 1966, by R. W. Walker, entitled Circulating Casing Hanger Assembly.
Another approach to casing sealing is to use two separate running tools, one to land a casing hanger, and the second to land a separate casing hanger seal assembly upon the top of the casing hanger member. By rotation of the running tool attached to the seal assembly, the casing hanger seal assembly is locked into place against the inner surface of the outer well head casing and the outer surface of the inner well head casing. Provision is then made to pressure test the assembled seal.
If a faulting seal is found, it will be necessary to remove the casing hanger seal assembly. Before this invention, when this necessity arose, the running tool which was used to assemble the casing hanger steel assembly was used by rotation in an opposite direction from its installation rotation to disassemble the seal. In this situation, it was hoped that the seal assembly would break loose and free itself before the drill pipe connection between the casing hanger member and the inner well head casing, for example, would break loose. When the seal assembly was not the first to break loose from its connection with the inner surface of the outer well head casing, substantial problems were created retrieving the seal.
One of the earliest solutions to the problem of retrieving a loose tool within a well is discussed in U.S. Pat. No. 1,737,305, which issued Nov. 26, 1929, by C. T. Flemming, entitled Fishing Tool Attachment. This patent discloses a fishing tool which includes a planetary gear arranged for providing a reversible direction of rotation to allow unscrewing of tools or pipes, other than oil well tools or pipes. This tool relies on wedges to engage the inner surface of a well casing. Once engaged, the wedges cause a reverse rotational motion to be transmitted through planetary gears to a center piece which threadably engages the tool to be retrieved. This tool does not lend itself to the retrieval of seal assemblies, however.
Other planetary gear devices have been proposed for use in disconnecting well pipes which employ a planetary gear, including: U.S. Pat. No. 1,627,842, issued May 10, 1927 by C. R. Edwards; U.S. Pat. No. 3,322,006, issued May 30, 1967 by C. C. Brown; and U.S. Pat. No. 3,434,543, issued Mar. 25, 1969 by D. D. Webb. None of these devices are designed to engage and retrieve a seal assembly. The releasing tool of the present invention was developed to assure proper engagement with a seal assembly and a timely release and retrieval thereof. Accordingly, an object of the present invention is to provide a seal assembly releasing tool which may be used to release the casing hanger seal assembly from engagement with the inner and outer surfaces of outer and inner well head casings.